1. Field of the Invention
The present invention relates to a zoom lens and an image pickup apparatus using the same.
2. Description of the Related Art
In video photography, capturing is carried out while zooming and focusing all the time. Zooming and focusing are carried out all the time means that lens groups of an optical system move all the time. As a lens group moves, a sliding sound is generated with the movement of the lens group. When the sliding sound is high, the sliding sound is recorded as a noise. Therefore, a zoom lens in which the number of lens groups which move is made smaller has been proposed.
As an example of the zoom lens in which, the number of lens groups is made smaller, a zoom lens which includes in order from an object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power, and in which, at the time of zooming, the first lens group is fixed, the second lens group moves to a side of an image plane, the third lens group is fixed, and the fourth lens group is moved, and the focusing is carried out by moving the fourth lens group has been proposed (Patent literature 1 to Patent literature 3).
Furthermore, a zoom lens in which a fifth lens group (fixed group) having a positive refractive power is added on an image side of the fourth lens group has been proposed (Patent literature 4 to Patent literature 7).    [Patent literature 1] Japanese Patent Application Laid-open Publication No. Sho. 62-178917    [Patent literature 2] Japanese Patent Application Laid-open Publication No. Sho. 63-29718    [Patent literature 3] Japanese Patent Application Laid-open Publication No. Sho. 63-123009    [Patent literature 4] Japanese Patent Application Laid-open Publication No. Hei. 3-154014    [Patent literature 5] Japanese Patent Application Laid-open publication No. Hei 5-264902    [Patent literature 6] Japanese Patent Application Laid-open Publication No. Hei 6-27375    [Patent literature 7] Japanese Patent Application Laid-open Publication No. Hei 7-151967